Back Flush Systems

What do they do?

After the milking of each individual cow, the back-flush unit cleans out the milk hose, claw and liners by rinsing the residue milk out with clean water, and then kills any remaining bacteria with an iodine solution.

By doing this on a systematic, automatic basis – after each and every cow – you can prevent infected milk from one cow touching the next cow… Thereby greatly reducing the chance of mastitis spreading from cow to cow.

System Components:

Back-Flush Slide Valve

The PBI Ross-Holm Back-Flush Slide Valve is an air pressure actuated valve that is compact in design, cleans properly and causes no bacteria problems in your milking system.

In designing this valve our main objectives were to keep it as simple as possible, use only the best materials for the job and refrain from sacrificing any quality just for ease of manufacturing or reducing the cost.

Apparently the valve was designed right the first time. It has been on the market since 1981 and no changes have been required.

The valve is easily adapted to any brand of equipment and lends itself extremely well for installations where space is limited. The compact size permits its use in parallel parlors as well as herringbone barns and others. The milk travels straight through the valve without restriction during milking thus preventing vacuum fluctuation. In addition the in-place wash up is very effective.

If a particular installation requires, the valve may be ordered with a 90° inlet or outlet or both as an option.

This Back-Flush Slide Valve works as a slide valve should. It has been in use at many large commercial dairies for well over 10 years.

Back-Flush Slide Valve - Construction

The enclosure and the lid are made of brushed stainless steel. The lid is easily removable for valve inspection.

The valve consists of an inlet and an outlet plate with a machined plastic slide sandwiched between them. The plastic slide is machined out 1/2 inch thick solid plate rather then molded.

The limitations of the molding process do not allow thick sections in plastic parts. This means that the back of the slide would have to include cavities. Since cavities are hard to clean, Ross Holm elected to stick with a machined part.

The inlet plate and the outlet plate are made of 1/4 inch thick stainless steel. After the inlet, outlet and iodine tubes are welded in, the surfaces of the plates are machined flat to match the flat surface of the plastic slide. By doing this we have made rubber seals unnecessary and thereby eliminated one of the major causes of bacteria build up.

The inlet plate is mounted solid to the enclosure with standoffs. The outlet plate is guided by these standoffs to stay aligned and is spring loaded against the slide and the inlet plate by four stainless steel springs.

The air cylinder that pushes the slide up into the milk position is made of stainless steel with a welded bottom. The piston is solid plastic and has the seal machined in. The rod is also made of plastic and is held captive by indents in the piston and the bottom of the slide. The whole assembly uses stainless steel hardware to circumvent corrosion.

Back-Flush Slide Valve - Operation

By applying air pressure to the cylinder on the bottom of the valve, the piston pushes the slide into the milk position. In the milk position the inlet and the outlet tubes are connected- straight through the slide. At the same time the iodine tube is vented out the bottom of the valve. This safety feature prevents iodine solution from entering the milk in case of a back flush control failure.

When the air pressure is removed from the cylinder the slide is forced back down into the back flush position by two stainless steel tension springs, one on each side of the slide. In this position the iodine tube is connected with the inlet tube, on the same side of the slide. The outlet tube is closed off on the other side of the slide. Due to the spacing of the connecting tubes the outlet tube can never be connected to the iodine tube and an atmospheric break is always present between the two, an essential fail safe design attribute.

Back-Flush Slide Valve - Features & Advantages

• Quality Materials
  
• Compact Size
  
• Cleans Every Time it Operates
  
• No Cheap Molded Parts
  
• No Rubber Seals
  
• All Stainless Repairable Air Cylinder
  
• No Milking Vacuum Restriction
  
• Adaptable to Any Brand System
  

Group Back-Flush Control

The Group Back-Flush Control for the back-flush was specifically designed for back-flushing a group of milking units at one time.

Parallel barns as well as herringbone barns require group flushing since all the cows on one side of the barn are released at the same time.

While the cows on the other side of the barn are milking, one group of cows is released and another group is allowed to enter. During this exchange time period the group back-flush system cleans out all the milking units, on that side of the barn, at once.

The Group Back-Flush Control consists of a stainless steel enclosure (11 in. wide by 14.5 in. high by 5.5 in. deep) with a light to indicate when a back-flush cycle is in process.

The enclosure contains: a control board with the sequence control electronics and pilot air valves, a pressure switch to sense the start signal, a 1 inch clean water valve, a 1 inch iodine water valve, a 1/2 inch air blow dry valve and a brass air valve to activate the slide valves. The entire assembly is tested on a test bench at the factory and is very easy to install.

The Group Back-Flush Control is capable of back-flushing up to 16 units. One Control is needed for each side of the barn and a slide valve is required for every cow milking position.

The Group Back-Flush Control can be signaled to start a back-flush cycle by either an air pressure signal (20-100 psi) or by an electrical contact closure. Once the cycle is started it can not, be interrupted until completely finished. A solid state electronic circuit controls the back flushing sequence. On the PC. board are the electronic components as well as the air pilot valves. The pilot valves are small three way valves that provide air pressure signals to the main water and air valves as the system is operating.

Group Back-Flush Control - Back-Flush Sequence

• Start signal received: Brass air valve is activated removing the air pressure from the slide valve cylinders, allowing them to shift to the back-flush position. Timing is adjustable from 1 to 6 seconds.
• The clean water valve is activated. This first rinse removes the remaining milk out of the milk hose and claw. Timing is adjustable from 3 to 20 seconds.

• **Note that during all the water cycles a small amount of air is released at the same time, this causes the water to become more turbulent and makes the flushing action more effective.**

• The clean water valve is closed and the iodine water valve is actuated. Water with iodine is used to kill any remaining bacteria. The iodine water flush is adjustable from 3 to 20 seconds.
• The iodine water valve is closed and the solution is allowed to remain in the hoses and claws to give the iodine enough time to work. This time is adjustable from 6 to 40 seconds.
• The clean water valve is now activated for a second rinse to remove the iodine solution from the system. Timing is adjustable from 3 to 20 seconds.
• The clean water valve is closed and the air blow dry valve is activated to blow the remaining water out of all the hoses and claws. Timing is adjustable from 3 to 20 seconds.
• The air blow dry valve is closed and the brass air valve shifts back to apply air pressure to all the slide valve cylinders moving them back to the milking position.

Group Back-Flush Control - Milk Sweep

To prevent the back-flush system from discarding all the milk in the milk hose after a detacher removes the milking unit from the cow, a milk sweep system may be used. Milk Sweep is available as an option with the PBI Ross-Holm Milk Pro.

Make a complete system with the Group Back-Flush Control and PBI Ross-Holm Slide Valves.

PBI Ross-Holm specializes in tailoring stalls for your specific operation. We have extensive expertise in design from small family dairies to large mega-dairies. In fact, we built and installed the milking stalls for one of the largest dairy in the world, located in Saudi Arabia!